Understanding the signaling mechanisms that pattern and maintain the human eye are critically important to the medical community. A considerable amount of work is directed to understanding the pattern formation that occurs in the vertebrate eye, with the mouse being the standard model organism. Although completely unexpected, over the last 10 years it has become increasingly evident that the fly eye shares many structural and patterning features with the vertebrate eye. Thus, the fly can be considered another model organism for studying vertebrate eye development. Work in this lab has examined how signals from the tissue directly surrounding fly retina induce peripheral specializations necessary for the functioning eye. Recently, the same phenomenon was shown to occur in the mouse, using the same class of signaling molecules. Here, Wnt signals from the tissue directly adjacent to the retina direct the formation of the ciliary body and the iris. Our goals here are to examine in fine detail the patterning mechanisms by which the peripheral specializations are produced in the fly eye. We will use fly genetics, molecular biology, histology and biochemistry to determine the exact nature of the signals released that organize the peripheral specializations. We will elucidate the genes or proteins that are specifically turned on in the peripheral regions, and how they interact to direct the differentiation of the specialized structures. The results accruing from this work can then be taken and examined in the mouse to further our general understanding of retinal differentiation and its implications for human disease and vision.